For combustor liners, turbine wings, heat exchangers, fins, boilers, heating furnaces, etc. of gas turbines and the like, with respect to promotion of heat transfer between fluid and solids in cooling, heating, heat exchanging, etc., various structures have been devised based on specifications required for the respective equipment.
For example, in combustors of gas turbines for electric power generation or the like, it is demanded to maintain required cooling-performance with low pressure loss level, which does not allow gas turbine efficiency to be deteriorated, and to maintain the reliability of structural strength. Moreover, from the viewpoint of consideration to environmental problems, it is demanded to reduce a discharge amount of nitrogen oxide (NOx) generated in the combustors. The cause of the generation of NOx includes the fact that, at the time of combustion, oxygen and nitrogen in air are maintained at a very high temperature. In order to prevent this to reduce NOx, premix combustion in which fuel and air are mixed prior to combustion and the mixture is then combusted is employed, and it is realized to combust the mixture in a state where the mixture ratio of fuel and air (a fuel-air ratio) is lower than a theoretical mixture ratio.
As a heat transfer device (a heat transfer structure) of a gas turbine combustor in which the above mentioned matter is taken into consideration, a structure provided with a combustor liner which is formed by axially connecting a plurality of cylindrical materials formed by cylindrically rolling up substantially rectangular-shaped plate materials is described in Japanese Patent Application Laid-Open No. 2001-280154 (Patent Literature 1). Each cylindrical material in the combustor liner is overlapped on and connected to adjacent cylindrical materials. The overlapped portions are coupled by welding or brazing.
Moreover, at one end of each cylindrical material (a downstream side in a flowing direction of compressed air from a compressor), a plurality of protrusions (longitudinal vortex generators) which are formed by press machining or the like are circumferentially arranged. The longitudinal vortex generators generate a longitudinal vortex which has a central rotation axis in a flowing direction of a cooling medium (cooling air) (compressed air). By the longitudinal vortex, the cooling medium (cooling air) in a flow passage is agitated. Moreover, on an outer peripheral surface of the combustor liner, ribs (turbulators) for destroying a boundary layer which is generated in the cooling medium (cooling air) agitated by the longitudinal vortex generators are provided.
Moreover, as a heat transfer structure of a gas turbine combustor which has a different structure, a structure is described in Japanese Patent Application Laid-Open No. Hei. 6-221562 (Patent Literature 2), in which an inner diameter of an outer tube provided for forming a flow passage for a cooling medium (cooling air) on the outside of a liner is gradually reduced. In the structure described in this literature, a heat transfer coefficient is improved by reducing the cooling medium flow passage between the combustor liner and the outer tube to increase a flow velocity of the cooling medium and by increasing surface roughness of a liner surface.
Moreover, as a heat transfer structure of a gas turbine combustor which has a different structure, a structure is described in Japanese Patent Application Laid-Open No. 2000-320837 (Patent Literature 3). This literature describes “by providing guide fins on an outer periphery side of a liner and on an inner periphery side of an outer tube, a flow velocity is increased to realize improvement in heat transfer effect”.
While the heat transfer device disclosed in the patent literature 1 is superior to conventional heat transfer devices in cooling performance, structural strength, low NOx property, and the like, there remains room for improvement in its structure from the viewpoint of the simplification of manufacturing process and long-life property.
For example, while the combustor liner is formed by axially coupling the plurality of cylindrical materials, the respective cylindrical materials are weld-coupled at the overlapped portions. Such welded portions may become the cause of generation of cracks and may not endure long usage as compared to a case where the welding is not employed (namely, in a case where the combustor liner is formed from a single cylindrical material). Moreover, the fact that the provision of a great number of welded portions increases the workload of the combustor liner to result in an increase in the manufacturing cost of the combustor liner can be pointed out. This fact becomes more remarkable in the case of employment of welding for the mounting of the ribs that are the turbulators.
Moreover, in the case of the employment of the welding, the respective cylindrical materials may be subjected to thermal deformation. In the case of occurrence of the thermal deformation, an incorporating property of the combustor liner into other cylindrical members (for example, a disk plate, to which a combustion nozzle and a premix nozzle are mounted, a transition piece (a tail cylinder), etc.) is lowered and the labor for causing the combustor liner to be again formed into a circular shape is required, whereby the fabrication process of the combustor may be complicated. Moreover, the fact that because the overlapped portions of the respective cylindrical materials forming the combustor liner have double structures and become thicker than other portions, the heat transfer property (cooling property) of the overlapped portions is lowered as compared to that of the other portions can be also pointed out.
Moreover, the heat transfer device disclosed in the patent literature 2 has a simple structure on the combustor liner side as compared to the heat transfer device disclosed in the patent literature 1, so that it is considered to be superior in the simplification of the fabrication process and the long-life property of the structure, but it realizes the heat transfer promotion only by the increase in the flow velocity and the surface roughness, so that the pressure loss may become excessively high in order to obtain a large heat transfer promoting effect.
Moreover, although the heat transfer device disclosed in the patent literature 3 has the structure in which the guide fins are installed only on the inner periphery side of the outer tube and which is superior in the simplifying property and the long-life property, the action in the heat transfer device which contributes to the heat transfer promoting is only the increase in the flow velocity and, like the heat transfer device described in the patent literature 2, the pressure loss may become excessively high in order to obtain the large heat transfer promoting effect.
The object of the present invention is to provide a heat transfer device which can promote heat transfer while suppressing an increase in pressure loss and is superior in a simplifying property of a fabrication process and a long-life property.